Prior to the reduction of a log into planks, beams, and like semifinished pieces, it is necessary to remove the bark, phloem, and other outside fibers from the log. This is usually effected by supporting the elongated log horizontally and rotating it on its longitudinal axis as a tool, such as described in U.S. Pat. No. 3,351,109, is displaced longitudinally relative to the log. This debarking tool rips off all of the bark and outer fibers from the rapidly rotating log as the log and the tool move relatively to each other longitudinally. It is known to displace the logs under a fixed tool, or to displace a tool the length of the fixed log.
As it is being debarked the log is usually supported in the nip between two sets of rotating wheels or disks which are each rotatable about a respective horizontal axis parallel to the axis of the other set. The disks are rotated in the same rotational sense and are spaced apart by a distance determined by the diameter of the log being treated.
A considerable disadvantage of this system is that it is necessary carefully to space the set of disks apart according to the log size. If they are spaced too far apart the log will drop down between them and if they are too close together the log will tend to jump off the apparatus.
Another disadvantage of this known system is that a log which is not relatively straight or is otherwise of uneven contours strikes the disks extremely hard at certain locations as it is rotated at high speed. This causes rapid wear of the machine, and even occasionally damages it so badly that it is necessary to stop the operation and repair or replace one of the disks before continuing.